Thermal recording materials

Abstract

To provide a heat-sensitive recording material that does not substantially contain a dye precursor or a developer, and offers superior whiteness, coloring density, and print suitability.SOLUTION: Disclosed is a heat-sensitive recording material comprising a support body including at least one colored surface, and a light-scattering layer disposed thereon. The light-scattering layer contains non-void polymer particles and a transparentizing agent. The content ratio of the non-void polymer particles is 25 to 60 mass% of the total solid amount of the light-scattering layer. The content ratio of the transparentizing agent is 10 to 40 mass% of the total solid amount of the light-scattering layer. The light-scattering layer does not substantially contain a dye precursor or a developer.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a thermal recording material. [Background technology]

[0002] Thermal recording materials that record colored images using a heating-induced color reaction between a colorless or light-colored dye precursor and phenols or organic acids are widely used. Because such thermal recording materials form colored images simply by heating, they offer advantages such as compact recording devices, easy maintenance, and low noise generation. Therefore, thermal recording materials are widely used as information recording materials in various applications, including label printers, automatic ticket vending machines, CD / ATM machines, order slip output machines in restaurants, and data output machines for scientific research equipment.

[0003] Other thermal recording materials besides those that utilize the color development reaction between a dye precursor and a color developer include, for example, the thermal recording material reported in Patent Document 1.

[0004] Patent Document 1 reports a recording material comprising a) a support having at least one colored surface; and b) a layer disposed thereon, wherein the layer comprises polymer particles having a core / shell structure and an opacity reducing agent having a melting point from 45°C to 200°C, in an amount from 1% to 90% by weight based on the weight of the polymer particles, wherein the particles have an outer first polymer shell having a calculated Tg from 40°C to 130°C, and the particles contain at least one void when dry.

[0005] In such thermal recording materials, the colored surface is concealed by an opaque layer. When heated, an opacity-reducing agent melts, causing the layer on the colored surface to become transparent, allowing the colored surface to be seen and thus enabling printing.

[0006] However, conventional thermal recording materials that substantially do not contain dye precursors and color developers have insufficient whiteness, color density, and printability, and there is room for improvement. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Special Publication No. 2014-512290 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] The main objective of this invention is to provide a thermal recording material that is substantially free of dye precursors and color developers, and that exhibits excellent whiteness, color density, and printability. [Means for solving the problem]

[0009] The inventors, after diligent research to solve the above-mentioned problems, have found that the above-mentioned problems can be solved by incorporating 25 to 60% by mass of polymer particles without hollows and 10 to 40% by mass of a transparency agent into the light scattering layer, and have completed the present invention. That is, the present invention relates to the following thermal recording material.

[0010] Item 1: A thermal recording material comprising a support including at least one colored surface and a light-scattering layer disposed thereon, wherein the light-scattering layer contains non-hollow polymer particles and a clearing agent, the proportion of the non-hollow polymer particles being 25 to 60% by mass of the total solid content of the light-scattering layer, the proportion of the clearing agent being 10 to 40% by mass of the total solid content of the light-scattering layer, and the light-scattering layer substantially free of dye precursors and color developers. Item 2: The thermal recording material according to Item 1, wherein the clearing agent contains at least one selected from the group consisting of stearic acid amide, palmitic acid amide, aromatic oxalic acid ester, aromatic ethylene glycol ether, ethylene-bis-stearic acid amide, 1,2-diphenyloxyethane, 1,2-di(3-methylphenoxy)ethane, dibenzyl oxalate, dibenzyl terephthalate, benzyl biphenyl, benzyl-2-naphthyl ether, diphenyl sulfone, m-terphenyl, p-benzyloxybenzyl benzoate, cyclohexanedimethanol benzoate, p-toluenesulfonamide, o-toluenesulfonamide, 2,6-diisopropylnaphthalene, 4,4-diisopropylbiphenyl, and erucic acid amide. Item 3: The thermal recording material according to Item 1, wherein the clearing agent contains at least one selected from the group consisting of stearic acid amide and palmitic acid amide. Item 4: The thermal recording material according to Item 1, wherein the clearing agent contains both stearic acid amide and palmitic acid amide. Item 5: The thermal recording material according to any one of items 1 to 4, wherein the content of the non-hollow polymer particles is 30 to 50% by mass of the total solid content of the light scattering layer. Item 6: The thermal recording material according to any one of items 1 to 5, wherein the content of the clearing agent is 20 to 35% by mass of the total solid content of the light scattering layer. Item 7: A thermal recording material according to any one of items 1 to 6, wherein the average particle size of the non-hollow polymer particles is 0.2 to 3.0 μm. Item 8: The thermal recording material according to any one of items 1 to 7, wherein the refractive index of the non-hollow polymer particles is 1.55 to 1.65. [Effects of the Invention]

[0011] The thermal recording material of the present invention is a thermal recording material that substantially does not contain a colorant precursor and a color developer, and is excellent in whiteness, color density and printability. [Modes for carrying out the invention]

[0012] In this specification, the expression "comprising" includes the concepts of "including", "consisting essentially of", and "consisting of only".

[0013] In this specification, the numerical range represented by "~" means a range including the numerical values described before and after "~" as the lower limit value and the upper limit value.

[0014] The latex in the present invention includes a gel or a dry film state formed by drying a dispersion medium.

[0015] In addition, in the present invention, "average particle diameter" refers to the volume-based median diameter measured by the laser diffraction method. More simply, an electron microscope can be used to measure the particle diameters from particle images (SEM images) respectively, and the average value of 10 can be shown.

[0016] The present invention is a heat-sensitive recording material having a support including at least one colored surface and a light-scattering layer disposed thereon, wherein the light-scattering layer contains polymer particles having no hollow and a clarifying agent, the content ratio of the polymer particles having no hollow is 25 to 60% by mass in the total solid content of the light-scattering layer, the content ratio of the clarifying agent is 10 to 40% by mass in the total solid content of the light-scattering layer, and the light-scattering layer substantially does not contain a dye precursor and a developer.

[0017] [Support] The support in the present invention is not particularly limited in terms of type, shape, dimensions, etc. For example, it can be appropriately selected and used from among fine paper (acidic paper, neutral paper), medium paper, coated paper, art paper, cast-coated paper, glassine paper, resin laminated paper, polyolefin-based synthetic paper, synthetic fiber paper, non-woven fabric, synthetic resin film, and various transparent supports, etc. In an embodiment of the present invention, the support may have a colored surface on one side or both sides may be colored. The color may be imparted, for example, by a pigment, a dye, or the inherent color of the support, and the support may be immersed in a colorant to provide a colored surface. The thickness of the support is not particularly limited and is usually about 20 to 200 μm. Also, the density of the support is not particularly limited, and a density of about 0.60 to 0.85 g / cm 3 is preferable.

[0018] [Colored surface] In the heat-sensitive recording material of the present invention, at least one colored surface is provided on the support. This enables printing when the light-scattering layer becomes transparent due to heat.

[0019] The support may have a colored surface on one side or on both sides. The colored surface only needs to have a sufficient color density that is visually contrastive with respect to the light-scattering layer disposed thereon. The colored surface may have a uniform color density, a varying color density, or may be patterned. The type of color of the colored surface is also not particularly limited and can be any color.

[0020] The colored surface may be a colored layer formed on the support. The colored layer can contain a dye, a pigment, carbon black, etc. as a colorant for imparting color. The content ratio of the colorant can be selected from a wide range, but generally, about 5 to 50% by mass, and more preferably about 7 to 30% by mass, of the total solid content of the colored layer is preferable.

[0021] The colored layer may contain pigments other than colorants. Examples of pigments include inorganic pigments such as calcium carbonate, magnesium carbonate, kaolin, calcined kaolin, clay, talc, calcined clay, silica, diatomaceous earth, synthetic aluminum silicate, zinc oxide, titanium oxide, aluminum hydroxide, barium sulfate, surface-treated calcium carbonate, silica, hollow polymer particles, and non-hollow polymer particles. The pigment content can be selected from a wide range, but generally, it is preferably about 30 to 80% by mass, and more preferably about 40 to 70% by mass, of the total solid content of the colored layer.

[0022] The colored layer is generally formed by applying and drying a coating solution for the colored layer onto a support, which is prepared by mixing and stirring a colorant, other pigments, adhesives, auxiliary agents, etc., with water as a medium. The amount of coating solution for the colored layer applied is not particularly limited, but is 2 to 15 g / m² by dry mass. 2 A suitable amount is 3-10 g / m². 2 A more moderate degree is preferable.

[0023] Examples of adhesives include water-soluble polymer materials such as polyvinyl alcohol and its derivatives, starch and its derivatives, cellulose derivatives such as hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, carboxymethylcellulose, methylcellulose, and ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylamide-acrylic acid ester copolymer, acrylamide-acrylic acid ester-methacrylic acid ester copolymer, styrene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, casein, gelatin and their derivatives, as well as emulsions such as polyvinyl acetate, polyurethane, polyacrylic acid, polyacrylic acid ester, vinyl chloride-vinyl acetate copolymer, polybutyl methacrylate, and ethylene-vinyl acetate copolymer, or latex of water-insoluble polymers such as styrene-butadiene copolymer and styrene-butadiene-acrylic copolymer. The content of the adhesive can be selected from a wide range, but generally it is preferably about 5 to 40% by mass, and more preferably about 10 to 30% by mass, of the total solid content of the colored layer.

[0024] [Light scattering layer] The thermal recording material of the present invention has a light-scattering layer on a colored surface. The light-scattering layer contains polymer particles that do not have voids and a clearing agent. Furthermore, the light-scattering layer substantially does not contain dye precursors and color developers.

[0025] (Polymer particles that do not have a hollow core) By including polymer particles without hollows, light scattering occurs in the light scattering layer, resulting in the concealment of the colored surface. Furthermore, using polymer particles without hollows results in superior color intensity compared to using polymer particles with hollows.

[0026] Resins that can be used for polymer particles without hollows generally include acrylic resins and polystyrene resins, with styrene-acrylic copolymers being particularly preferred.

[0027] The average particle size of the polymer particles without hollows in this invention is preferably 0.1 to 5.0 μm, more preferably 0.2 to 3.0 μm, and even more preferably 0.4 to 2.0 μm. Here, the average particle size is the median diameter, which is the diameter at which the volume occupied by the larger particles and the smaller particles are equal when the particles are divided into two groups by particle size, i.e., the particle size at which the 50% volume frequency occurs, and is also referred to as D50. The average particle size (D50) of the polymer particles without hollows can be measured using a laser diffraction particle size distribution analyzer. Alternatively, the particle size may be measured from particle images (SEM images) using an electron microscope, and the average value of 10 particles may be shown. When the average particle size of the polymer particles without hollows is 0.1 to 5.0 μm, the whiteness of the thermal recording material can be improved.

[0028] The refractive index of the non-hollow polymer particles in this invention is preferably 1.55 to 1.65, more preferably 1.57 to 1.63, and even more preferably 1.57 to 1.60. Here, the refractive index can be measured by JIS K7142 Method B (Becke line method) or the like. If the refractive index of the non-hollow polymer particles is 1.55 or higher, the whiteness of the thermal recording material can be improved. On the other hand, if the refractive index of the non-hollow polymer particles is 1.65 or lower, the color intensity of the thermal recording material can be increased.

[0029] In the present invention, the content of non-hollow polymer particles is 25 to 60% by mass of the total solid content of the light scattering layer, preferably 30 to 50% by mass, and more preferably 35 to 50% by mass. When the content of non-hollow polymer particles is 25% by mass or more, the whiteness of the thermal recording material can be improved. On the other hand, when the content of non-hollow polymer particles is 60% by mass or less, the color intensity can be increased.

[0030] (Clearing agent) By including a clearing agent, when heat is applied, the clearing agent melts, changing the refractive index of the light scattering layer. As a result, the light scattering layer becomes transparent, and the colored surface becomes visible.

[0031] Specific examples of clearing agents include stearic acid amide, palmitic acid amide, aromatic oxalic acid ester, aromatic ethylene glycol ether, ethylene-bis-stearic acid amide, 1,2-diphenyloxyethane, 1,2-di(3-methylphenoxy)ethane, dibenzyl oxalate, dibenzyl terephthalate, benzyl biphenyl, benzyl-2-naphthyl ether, diphenyl sulfone, m-terphenyl, p-benzyloxybenzyl benzoate, cyclohexanedimethanol benzoate, p-toluenesulfonamide, o-toluenesulfonamide, 2,6-diisopropylnaphthalene, 4,4-diisopropylbiphenyl, and erucic acid amide. Of course, the agents are not limited to these, and two or more compounds can be used in combination as needed.

[0032] Among the clearing agents, stearic acid amide and palmitic acid amide are preferred from the viewpoint of excellent printability, and using stearic acid amide and palmitic acid amide in combination is particularly preferred because it can increase the color intensity.

[0033] The content of the transparentizing agent is 10 to 40% by mass of the total solid content of the light scattering layer, preferably 20 to 35% by mass, and more preferably 20 to 30% by mass. A content of 10% by mass or more can increase the color intensity. A content of 40% by mass or less can improve printability.

[0034] The content of the clearing agent is preferably 0.2 parts by mass or more, and more preferably 0.4 parts by mass or more, per 1 part by mass of non-hollow polymer particles. On the other hand, the content of the clearing agent is preferably 2.0 parts by mass or less, and more preferably 1.6 parts by mass or less, per 1 part by mass of non-hollow polymer particles.

[0035] (Hollow polymer particles) By including hollow polymer particles, light scattering occurs in the light scattering layer, resulting in the concealment of the colored surface.

[0036] While polymer particles with hollow structures offer better opacity of colored surfaces than polymer particles without hollow structures, their color intensity is lower than that of polymer particles without hollow structures.

[0037] Adhesives can be used as other component materials for the light scattering layer, and additional auxiliary agents such as crosslinking agents, lubricants, water-resistant agents, and dispersants can be used as needed.

[0038] Examples of adhesives include water-soluble polymer materials such as polyvinyl alcohol and its derivatives, starch and its derivatives, cellulose derivatives such as hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, methylcellulose, and ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylamide-acrylic acid ester copolymer, acrylamide-acrylic acid ester-methacrylic acid ester copolymer, styrene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, casein, gelatin and their derivatives, as well as emulsions such as polyvinyl acetate, polyurethane, polyacrylic acid, polyacrylic acid ester, vinyl chloride-vinyl acetate copolymer, polybutyl methacrylate, and ethylene-vinyl acetate copolymer, or water-insoluble polymer latex such as styrene-butadiene copolymer and styrene-butadiene-acrylic copolymer. Among these, polyvinyl alcohol and latex are preferred. The content of the adhesive can be selected from a wide range, but generally it is preferably about 7 to 50% by mass, and more preferably about 10 to 45% by mass, of the total solid content of the light scattering layer.

[0039] By incorporating a crosslinking agent into the light scattering layer, the water resistance of the light scattering layer can be improved. Examples of crosslinking agents include aldehyde compounds such as glyoxal, polyamine compounds such as polyethyleneimine, epoxy compounds, polyamide resins, melamine resins, glyoxylates, dimethylolurea compounds, aziridine compounds, and blocked isocyanate compounds; inorganic compounds such as ammonium persulfate, ferric chloride, magnesium chloride, sodium tetraborate, and potassium tetraborate; boric acid, trysterol borate, boron-based polymers, hydrazide compounds, and glyoxylates. These may be used individually or in combination of two or more.

[0040] Metallic soaps may be used as lubricants. Examples of metallic soaps include polyvalent metal salts of higher fatty acids, namely zinc stearate, aluminum stearate, calcium stearate, and zinc oleate.

[0041] The light scattering layer is formed on a colored surface by, for example, dispersing a clearing agent with water as the dispersion medium using various stirring and wet grinding machines such as ball mills, co-ball mills, attritors, and vertical and horizontal sand mills, along with water-soluble synthetic polymer compounds such as polyacrylamide, polyvinylpyrrolidone, polyvinyl alcohol, methylcellulose, and styrene-maleic anhydride copolymer salts, and other surfactants, and then finely grinding each dispersion to an average particle size of 2 μm or less, and mixing in polymer particles that do not have hollows with the obtained dispersion, and if necessary, mixing in adhesives, auxiliary agents, etc. The coating solution for the light scattering layer is applied and dried. The amount of coating solution for the light scattering layer applied is not particularly limited, and the amount applied after drying is 1 to 15 g / m². 2 A suitable amount is 2-10 g / m². 2 A more preferable degree is 2.5-8 g / m 2 A more preferable degree is 3-5 g / m 2 The degree is particularly preferable. The light scattering layer can be formed in two or more layers as needed, and the composition and coating amount of each layer may be the same or different.

[0042] [Protective Layer] In a thermal recording material, a protective layer can also be provided on the light scattering layer as needed. The protective layer preferably contains a pigment and an adhesive. Further, it is preferable to contain a lubricant such as polyolefin wax or zinc stearate in the protective layer for the purpose of preventing sticking to the thermal head, and an ultraviolet absorber can also be contained. Also, by providing a protective layer having gloss, the added value of the product can be increased.

[0043] The pigment contained in the protective layer is not particularly limited, and examples thereof include inorganic pigments such as amorphous silica, kaolin, clay, light calcium carbonate, heavy calcium carbonate, calcined kaolin, titanium oxide, magnesium carbonate, aluminum hydroxide, colloidal silica, synthetic phyllosilicate, and plastic pigments such as urea-formalin resin filler.

[0044] The adhesive contained in the protective layer is not particularly limited, and a water-soluble or water-dispersible aqueous adhesive can be used. The adhesive can be appropriately selected from those that can be used for the light scattering layer. Among these adhesives, various modified polyvinyl alcohols such as acetoacetyl-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, and diacetone-modified polyvinyl alcohol are more preferably used.

[0045] The protective layer is formed, for example, by applying a coating liquid for the protective layer prepared by mixing a pigment, an adhesive, and, if necessary, auxiliaries, etc. with water as a dispersion medium, and then drying it on the light scattering layer. The coating amount of the coating liquid for the protective layer is not particularly limited, and a dry mass of 0.3 to 15 g / m 2 is preferable, 0.3 to 10 g / m 2 is more preferable, 0.5 to 8 g / m 2 is even more preferable, 1 to 8 g / m 2 is particularly preferable, 1 to 5 g / m 2 is even more preferable. Note that the protective layer can be formed in two or more layers as needed, and the composition and coating amount of each layer may be the same or different.

[0046] [Other layers] In the present invention, it is preferable to have an adhesive layer on at least one side of the support. This can increase the added value of the thermal recording material. As the adhesive layer, for example, by applying an adhesive, re-wettable adhesive, delayed-tack type adhesive, etc. to one side, adhesive paper, re-wettable adhesive paper, delayed-tack paper, etc. can be made. Alternatively, by utilizing the side of the support opposite to the light scattering layer and imparting it functions as thermal transfer paper, inkjet recording paper, carbonless paper, electrostatic recording paper, zeography paper, etc., it is possible to make recording paper that can record on both sides. Of course, it can also be a double-sided thermal recording material. Furthermore, a back layer can be provided to suppress the penetration of oil and plasticizer from the back surface of the thermal recording material, control curl, and prevent static charge. It is also possible to make a linerless label that does not require release paper by applying a release layer containing silicone on the protective layer and applying an adhesive to one side.

[0047] [Thermal recording material] The thermal recording material can be manufactured by forming the above-mentioned layers on a support. Any known coating method can be used to form the above-mentioned layers on the support, such as the air knife method, blade method, gravure method, roll coater method, spray method, dip method, bar method, curtain method, slot die method, slide die method, or extrusion method. In addition, each coating may be applied and dried one layer at a time to form each layer, or the same coating may be applied in two or more layers. Furthermore, simultaneous multilayer coating, in which two or more layers are applied at the same time, may be performed. In addition, after each layer has been formed, or at any stage after all layers have been formed, a smoothing treatment can be performed using a known method such as a supercalender or softcalender. [Examples]

[0048] The present invention will be described in more detail by reference to examples, but the present invention is not limited thereto. Unless otherwise specified, "parts" and "%" refer to "parts by mass" and "mass%", respectively. The average particle size was measured using a laser diffraction particle size distribution analyzer SALD2200 (manufactured by Shimadzu Corporation). Here, the average particle size is the median diameter (D50).

[0049] The refractive index of polymer particles without hollow structures was measured under the following conditions. • Test method: JIS K7142 Method B (Becke's wire method) Measurement conditions: Immersion solution; potassium tetraiodomercury(II) aqueous solution Test temperature: 23℃ Light source: Uses Na light source (D line / 589nm) • Equipment used: Abbe refractometer 2T (manufactured by Atago Corporation) Compact measuring microscope STM5-311 (manufactured by Olympus, observation magnification 400x)

[0050] (Example 1) (1) Preparation of coating solution for colored layer A coating solution for a colored layer was obtained by mixing a composition consisting of 169.8 parts of a plastic hollow particle dispersion (product name: Lowpake SN-1055, hollowness ratio: 55%, average particle size: 1.0 μm, manufactured by Dow Chemical, solid content concentration 26.5% by mass), 40.0 parts of a 50% aqueous dispersion of calcined kaolin (product name: Ansilex 93, manufactured by BASF) (average particle size: 0.6 μm), 41.7 parts of styrene-butadiene latex (product name: L-1571, manufactured by Asahi Kasei Chemicals, solid content concentration 48% by mass), 50.0 parts of a 10% aqueous solution of oxidized starch, 26.3 parts of a carbon black dispersion (product name: Black FLTB, manufactured by Dainichi Seika Kogyo Co., Ltd., solid content concentration 38.0%), and 20 parts of water.

[0051] (2) Preparation of fatty acid amide dispersion 12.5 parts stearic acid amide, 12.5 parts palmitic acid amide, 25.0 parts a 10% aqueous solution of partially saponified PVA (product name: Kuraray Poval 5-88, manufactured by Kuraray Co., Ltd.), and 50 parts water were mixed and ground using a sand mill (manufactured by AIMEX, sand grinder) until the median diameter measured by a laser diffraction particle size analyzer SALD2200 (manufactured by Shimadzu Corporation) was 1.0 μm to obtain a clarifying agent dispersion.

[0052] (3) Preparation of coating solution for light scattering layer A coating solution for a light scattering layer was obtained by mixing a composition consisting of 75.5 parts of a polymer particle dispersion without hollows (product name: Grossdale 130S, average particle size 0.7 μm, manufactured by Mitsui Chemicals, solid content concentration 53.0% by mass, refractive index 1.58), 100.0 parts of the fatty acid amide dispersion obtained in (2), 225.0 parts of a 10.0% aqueous solution of fully saponified PVA (product name: Kuraray Poval 11-98, manufactured by Kuraray Co., Ltd.), 27.8 parts of an aqueous dispersion of zinc stearate (product name: Hydrin Z-9-36, manufactured by Chukyo Oil & Fat Co., Ltd., solid content concentration 36.0%), and 50.0 parts of water.

[0053] (4) Preparation of thermal recording material Basis weight 42g / m 2 On one side of the high-quality paper, the coating liquid for the colored layer and the coating liquid for the light scattering layer were applied at a dry amount of 6.0 g / m² each. 2 5.0g / m 2 The material was coated and dried in such a manner to sequentially form a colored layer and a light scattering layer, thereby obtaining a thermal recording material.

[0054] (Example 2) In preparing the coating solution for the light scattering layer in Example 1, the amount of a polymer particle dispersion without hollows (product name: Grossdale 130S, average particle size 0.7 μm, manufactured by Mitsui Chemicals, Inc., solid content concentration 53.0% by mass, refractive index 1.58) was changed from 75.5 parts to 47.2 parts, and the amount of a 10.0% aqueous solution of fully saponified PVA (product name: Kuraray Poval 11-98, manufactured by Kuraray Co., Ltd.) was changed from 225.0 parts to 375.0 parts. Otherwise, a thermal recording material was obtained in the same manner as in Example 1.

[0055] (Example 3) In preparing the coating solution for the light scattering layer in Example 1, the amount of a polymer particle dispersion without hollows (product name: Grossdale 130S, average particle size 0.7 μm, manufactured by Mitsui Chemicals, Inc., solid content concentration 53.0% by mass, refractive index 1.58) was changed from 75.5 parts to 113.2 parts, and the amount of a 10.0% aqueous solution of fully saponified PVA (product name: Kuraray Poval 11-98, manufactured by Kuraray Co., Ltd.) was changed from 225.0 parts to 25.0 parts. Otherwise, a thermal recording material was obtained in the same manner as in Example 1.

[0056] (Example 4) In the preparation of the coating solution for the light scattering layer in Example 1, the amount of the fatty acid amide dispersion obtained in (2) was changed from 100.0 parts to 160.0 parts, and the amount of the 10.0% aqueous solution of fully saponified PVA (product name: Kuraray Poval 11-98, manufactured by Kuraray Co., Ltd.) was changed from 225.0 parts to 60.0 parts. Otherwise, a thermal recording material was obtained in the same manner as in Example 1.

[0057] (Example 5) In preparing the coating solution for the light scattering layer in Example 1, the amount of the fatty acid amide dispersion obtained in (2) was changed from 100.0 parts to 40.0 parts, and the amount of the 10.0% aqueous solution of fully saponified PVA (product name: Kuraray Poval 11-98, manufactured by Kuraray Co., Ltd.) was changed from 225.0 parts to 390.0 parts. Otherwise, a thermal recording material was obtained in the same manner as in Example 1.

[0058] (Example 6) A thermal recording material was obtained in the same manner as in Example 1, except that the amount of stearic acid amide was changed from 12.5 parts to 25.0 parts and the amount of palmitic acid amide was changed from 12.5 parts to 0 parts in the preparation of the fatty acid amide dispersion of Example 1.

[0059] (Example 7) A thermal recording material was obtained in the same manner as in Example 1, except that the amount of stearic acid amide was changed from 12.5 parts to 0 parts, and the amount of palmitic acid amide was changed from 12.5 parts to 25.0 parts.

[0060] (Example 8) In preparing the coating solution for the light scattering layer in Example 1, a thermal recording material was obtained in the same manner as in Example 1, except that 56.8 parts of a clearing agent dispersion prepared by the procedure in (5) below were used instead of 100.0 parts of the fatty acid amide dispersion obtained in (2).

[0061] (5) Preparation of the clearing agent dispersion 44 parts of di-p-methylbenzyl oxalate, 44 parts of a 10% aqueous solution of partially saponified PVA (product name: Kuraray Poval 5-88, manufactured by Kuraray Co., Ltd.), and 12 parts of water were mixed and ground using a sand mill (Aimex Co., Ltd., sand grinder) until the median diameter measured by a laser diffraction particle size analyzer SALD2200 (Shimadzu Corporation) was 1.0 μm to obtain a clarifying agent dispersion.

[0062] (Example 9) A thermal recording material was obtained in the same manner as in Example 8, except that diphenyl sulfone was used instead of di-p-methylbenzyl oxalate in the preparation of the clarifying agent dispersion of Example 8.

[0063] (Example 10) A thermal recording material was obtained in the same manner as in Example 8, except that 1,2-di(3-methylphenoxy)ethane was used instead of di-p-methylbenzyl oxalate in the preparation of the clearing agent dispersion of Example 8.

[0064] (Example 11) In preparing the coating solution for the light scattering layer in Example 1, the amount of the fatty acid amide dispersion obtained in (2) was changed from 100.0 to 40 parts, and 34.1 parts of the clearing agent dispersion prepared in the procedure of (5) were added. Otherwise, a thermal recording material was obtained in the same manner as in Example 1.

[0065] (Example 12) In preparing the coating solution for the light scattering layer in Example 1, 114.3 parts of a non-hollow polymer particle dispersion (product name: Grossdale 204S, average particle size: 0.2 μm, manufactured by Mitsui Chemicals, solid content concentration: 53.0% by mass, refractive index: 1.58) were used instead of 75.5 parts of the non-hollow polymer particle dispersion (product name: Grossdale 130S, average particle size: 0.7 μm, manufactured by Mitsui Chemicals, solid content concentration: 53.0% by mass, refractive index: 1.58). Otherwise, a thermal recording material was obtained in the same manner as in Example 1.

[0066] (Example 13) In preparing the coating solution for the light scattering layer in Example 1, 137.0 parts of a non-hollow polymer particle dispersion (product name: Saibinol PG-5, average particle size: 3.0 μm, manufactured by Saiden Chemical Co., Ltd., solid content concentration: 29.2 mass%, refractive index: 1.58) were used instead of 75.5 parts of a non-hollow polymer particle dispersion (product name: Grossdale 130S, average particle size: 0.7 μm, manufactured by Mitsui Chemicals, Inc., solid content concentration: 53.0 mass%, refractive index: 1.58). Otherwise, a thermal recording material was obtained in the same manner as in Example 1.

[0067] (Example 14) In preparing the coating solution for the light scattering layer in Example 1, 150.9 parts of a non-hollow polymer particle dispersion (product name: Saibinol PG-2, average particle size: 5.0 μm, manufactured by Saiden Chemical Co., Ltd., solid content concentration: 26.5 mass%, refractive index: 1.58) were used instead of 75.5 parts of a non-hollow polymer particle dispersion (product name: Grossdale 130S, average particle size: 0.7 μm, manufactured by Mitsui Chemicals, Inc., solid content concentration: 53.0 mass%, refractive index: 1.58). Otherwise, a thermal recording material was obtained in the same manner as in Example 1.

[0068] (Example 15) In preparing the coating solution for the light scattering layer in Example 1, a thermal recording material was obtained in the same manner as in Example 1, except that 200.0 parts of an aqueous dispersion of non-hollow polymer particles (product name: Epostor MV1002, average particle size: 2.0 μm, manufactured by Nippon Shokubai Co., Ltd., refractive index: 1.51) (solid content concentration: 20.0 mass) were used instead of 75.5 parts of a dispersion of non-hollow polymer particles (product name: Epostor MV1002, average particle size: 2.0 μm, manufactured by Nippon Shokubai Co., Ltd., refractive index: 1.51).

[0069] (Example 16) In preparing the coating solution for the light scattering layer in Example 1, a thermal recording material was obtained in the same manner as in Example 1, except that 200.0 parts of an aqueous dispersion of non-hollow polymer particles (product name: Epostor MS, average particle size 2.0 μm, manufactured by Nippon Shokubai Co., Ltd., refractive index 1.66) (solid content concentration 20.0 mass%) was used instead of 75.5 parts of a dispersion of non-hollow polymer particles (product name: Grossdale 130S, average particle size 0.7 μm, manufactured by Mitsui Chemicals, Inc., solid content concentration 53.0 mass%, refractive index 1.58).

[0070] (Comparative Example 1) In preparing the coating solution for the light scattering layer in Example 1, 135.6 parts of a plastic hollow particle dispersion (product name: Lowpake UltraE, hollowness ratio: 44%, average particle size: 0.4 μm, manufactured by Dow Chemical, solid content concentration: 29.5 mass) were used instead of 75.5 parts of a polymer particle dispersion without hollows (product name: Grossdale 130S, average particle size: 0.7 μm, manufactured by Mitsui Chemicals, Inc., solid content concentration: 53.0 mass) to obtain a thermal recording material in the same manner as in Example 1.

[0071] (Comparative Example 2) In preparing the coating solution for the light scattering layer in Example 1, the amount of a polymer particle dispersion without hollows (product name: Grossdale 130S, average particle size 0.7 μm, manufactured by Mitsui Chemicals, Inc., solid content concentration 53.0% by mass, refractive index 1.58) was changed from 75.5 parts to 28.3 parts, and the amount of a 10.0% aqueous solution of fully saponified PVA (product name: Kuraray Poval 11-98, manufactured by Kuraray Co., Ltd.) was changed from 225.0 parts to 475.0 parts. Otherwise, a thermal recording material was obtained in the same manner as in Example 1.

[0072] (Comparative Example 3) In preparing the coating solution for the light scattering layer in Example 1, the amount of a polymer particle dispersion without hollows (product name: Grossdale 130S, average particle size 0.7 μm, manufactured by Mitsui Chemicals, Inc., solid content concentration 53.0% by mass, refractive index 1.58) was changed from 75.5 parts to 122.6 parts, and the amount of a 10.0% aqueous solution of fully saponified PVA (product name: Kuraray Poval 11-98, manufactured by Kuraray Co., Ltd.) was changed from 225.0 parts to 25.0 parts. Otherwise, a thermal recording material was obtained in the same manner as in Example 1.

[0073] (Comparative Example 4) In the preparation of the coating solution for the light scattering layer in Example 1, the amount of the fatty acid amide dispersion obtained in (2) was changed from 100.0 parts to 20.0 parts, and the amount of the 10.0% aqueous solution of fully saponified PVA (product name: Kuraray Poval 11-98, manufactured by Kuraray Co., Ltd.) was changed from 225.0 parts to 445.0 parts. Otherwise, a thermal recording material was obtained in the same manner as in Example 1.

[0074] (Comparative Example 5) In preparing the coating solution for the light scattering layer in Example 1, the amount of the fatty acid amide dispersion obtained in (2) was changed from 100.0 parts to 180.0 parts, and the amount of the 10.0% aqueous solution of fully saponified PVA (product name: Kuraray Poval 11-98, manufactured by Kuraray Co., Ltd.) was changed from 225.0 parts to 5.0 parts. Otherwise, a thermal recording material was obtained in the same manner as in Example 1.

[0075] The above examples and comparative examples were evaluated using the following method. The results are shown in Table 1.

[0076] [ISO whiteness] Four layers of the obtained thermal recording material were stacked, and the ISO whiteness was measured using a colorimeter SC-WT (manufactured by Suga Test Instruments Co., Ltd.). An ISO whiteness of 35 or higher is required, and 40 or higher is desirable.

[0077] [Print density] Using a thermal recording evaluation machine (product name: TH-PMD, manufactured by Okura Electric Co., Ltd.), each thermal recording material was recorded with an applied energy of 0.24 mJ / dot, and the resulting printed area was measured in visual mode using a Macbeth densitometer (RD-914, manufactured by Macbeth Corporation). A higher value indicates a higher print density, and a recording density of 1.30 or higher is required, with 1.40 or higher being desirable.

[0078] [Printability] Using a thermal printer (product name: Lesprit T-408v-ex, manufactured by Sato Corporation), a solid black area of ​​18 cm was printed six times at an applied energy of 3 A, and the amount of printhead residue adhering to the thermal head was determined according to the following criteria. ○: The amount of residue on the head is very small, and it is at a level that does not cause any problems in actual use. △: Some residue is generated on the head, but it is at a level that does not cause problems in actual use. ×: A large amount of printhead residue was generated, causing printing problems. This is a level that is problematic for practical use.

[0079] [Table 1]

Claims

1. A thermal recording material comprising a support including at least one colored surface, and a light-scattering layer disposed thereon, wherein the light-scattering layer contains non-hollow polymer particles and a clearing agent, the proportion of the non-hollow polymer particles being 25 to 60% by mass of the total solid content of the light-scattering layer, the proportion of the clearing agent being 10 to 40% by mass of the total solid content of the light-scattering layer, and the light-scattering layer substantially free of dye precursors and color developers. A thermal recording material wherein the clearing agent contains at least one selected from the group consisting of stearic acid amide, palmitic acid amide, aromatic oxalic acid ester, aromatic ethylene glycol ether, ethylene-bis-stearic acid amide, 1,2-diphenyloxyethane, 1,2-di(3-methylphenoxy)ethane, dibenzyl oxalate, dibenzyl terephthalate, benzyl biphenyl, benzyl-2-naphthyl ether, diphenyl sulfone, m-terphenyl, p-benzyloxybenzyl benzoate, cyclohexanedimethanol benzoate, p-toluenesulfonamide, o-toluenesulfonamide, 2,6-diisopropylnaphthalene, 4,4-diisopropylbiphenyl, and erucic acid amide.

2. The thermal recording material according to claim 1, wherein the clearing agent contains at least one selected from the group consisting of stearic acid amide and palmitic acid amide.

3. The thermal recording material according to claim 1, wherein the clearing agent contains both stearic acid amide and palmitic acid amide.

4. The thermal recording material according to any one of claims 1 to 3, wherein the content of the non-hollow polymer particles is 30 to 50% by mass of the total solid content of the light scattering layer.

5. The thermal recording material according to any one of claims 1 to 3, wherein the content of the transparentizing agent is 20 to 35% by mass of the total solid content of the light scattering layer.

6. The thermal recording material according to any one of claims 1 to 3, wherein the average particle size of the polymer particles that do not have a hollow is 0.2 to 3.0 μm.

7. The thermal recording material according to any one of claims 1 to 3, wherein the refractive index of the polymer particles that do not have a hollow space is 1.55 to 1.65.

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